Electron discharge device



Aug. 21, 1951 J. s. DONAL, JR 2,565,357

ELECTRON DISCHARGE DEVICE Filed June 30, 1948 5 Sheets-Sheet 2 Summer .Jm-m S. DUNAL, TR

Gltorueg Aug. 21, 1951 J. s. DONAL, JR 5 I ELECTRON DISCHARGE DEVICE Filed June 30. 1948 3 Sheets-Sheet 3 Summer Juan 3. DENALJR.

Patented Aug. 21, 1951 2,565,357 ELECTRON mscnaaca nsvrce John S. Donal, Jr., Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application June 30, 1948, Serial No. 36,252

1 20 Claims.

This invention relates generally to radio frequency coupling systems and electron discharge devices therefor, and more particularly to electron discharge coupling devices utilizing a spiral electron beam for transferring radio frequency energy. The invention provides a novel method and means for changing the energy level in such devices.

In a copending application of Carmen L. Cuccia, Serial No. 754,756, filed June 14, 1947, now Patent No. 2,542,797, dated February 20, 1951, assigned to the same assignee as the instant application, there is described a microwave coupling device utilizing a grid-controlled spiral electron beam for amplitude modulating and transferring microwave energy from an oscillator to a load circuit. In this device an electron beam generated by an electron gun is projected along a constant magnetic field and through a transverse uniform microwave electric field, such as that set up between a pair of deflection plates connected to a source of microwave energy. The strength H of the magnetic field is adjusted to a value such that the angular rotation frequency of an electron in said field is equal to u, where e and m are the charge and mass of an electron and w is the angular frequency of the microwave energy applied to the deflection plates.

Under these conditions, as the electron beam passes through the transverse oscillating electric field it absorbs energy therefrom, all of the electrons revolving around the longitudinal axis of the device in synchronism with the electric field and traversing spiral paths having radii proportional to the energy absorbed from" the electric 'field, and having axial velocities proportional to the axial electron beam accelerating potential. Since they have the same angular and axial velocities, all the spirally traveling electrons in the beam lie at any instant on the linear directrix of a cone, and the envelope of the rotating beam is a cone. Hence, the beam-is sometimes termed a "rotating pencil" beam. When the electrons emerge from the electric field and continue in the constant magnetic field the path of each electron becomes a helix of constant radius, since the centrifugal force due to the energy acquired from the electric field is balanced by the focusing effect of the magnetic field, and the rotating beam becomes a, cylinder-directrix pencil beam with a cylindrical envelope.

The rotating pencil beam is then projected 12 through an output system, which may be a pair of fiat plates similar to the input plates and connected to a load circuit resonant at the operatim frequency. As the electrons revolve around the axis of rotation of the beam they induce microwave potentials on the output plates and thus deliver energy thereto at the operating frequency. As energy is abstracted from the beam the radii of the electron paths are reduced as a function of energy abstraction, because of the focusing effect of the magnetic field, and hence. the electrons traverse spiral paths of decreasing radii, the beam envelope being conical. After delivering energy to the output system, the beam is collected by a collector electrode. By applying modulating signals or control potentials to the control grid of the electron beam gun the intensity of the beam can be varied, which results in a corresponding variation in the effective coupling factor between the input and output circuits, thus providing amplitude modulation of the input microwave signals.

The coupling device Just described is useful for modulating and transferring energy from one circuit to another. However, it is also desirable to incorporate in such a device means for amplifying the energy being transferred. Therefore, the principal object of my invention is to provide an electron discharge device utilizing a spiral electron beam for transferring radio frequency energy with means for amplifying such energy during transfer thereof. Another object is to devise means which may be employed either to amplify a modulated or unmodulated signal, to amplify and also amplitude modulate a signal, or to amplitude modulate a signal without amplification. Another object is to provide a spiral beam type electron discharge device with novel means for changing or varying the energy level of the spiralling electrons. Another object is to provide a novel signal amplifying means which is substantially independent of the amplitude of the signal. Still another object is to provide means for varying the cross-sectional area of an electron beam in combination with means for intercepting a portion of the beam. Another object of the invention is to design an improved electron discharge device especially adapted to modulate a high frequency signal.

A feature of the invention is the projection of an electron beam possessing spiral energy through a radial electric field to change the total energy of the beam, either by the injection of energy from said field into said beam, thereby increasing the spiral radii of the electrons, or

by the extraction of energy from the beam by said field, depending upon the direction of the radial field.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best'be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a longitudinal section view, partly schematic, of one embodiment of an electron discharge device amplifier incorporating my invention; Figs. 2 and 3 are transverse sectional views taken on the lines 22 and 3-3 respectively of Fig. l Fig. 4 is a transverse view taken on the same plane as Fig.

3 showing on an enlarged scale the axial projection of a half cycle of the paths of four electrons spaced along the beam at quarter cycle intervals; Fig. 5 is a view similar to Fig. 1 of a modification of my invention; Fig. 6 is a plan view of an alternative cut-off ring; Fig. 7 is a fragmentary view showing a further modification; Fig. 8 is a longitudinal section view of a practical structure embodying my invention as a modulating means in an electron coupler utilizing cavity resonators; and Figs. 9 and 10 are transverse sectional views taken on the lines 9-9 and l||||l, respectively, of Fig. 8. 7

Referring first to Figs. 1-4, there is shown an electron discharge device having an elongated envelope Within the envelope I, spaced along a central axis ZZ, are mounted by suitable means an electron gun comprising a cathode 2, heater 3, cathode shield 4, control grid 5, and apertured accelerating and beam forming electrode i, a pair of parallel flat plates 9 and I spaced on opposite sides of the central axis, a second pair of parallel fiat plates H and I! also on opposite sides of the central axis, and a collector plate I3. A constant magnetic field of proper strength extending along the central axis ZZ is established within the envelope throughout the length of the beam path by any suitable means, such as the electromagnet coil l shown. The structure described thus far is similar tothe modulating electron coupler disclosed in the above mentioned Cuccia application. In operation, a radio frequency electric field E sin wt is set up between the plates 9 and Ill, by an oscillator connected to an input transformer ||i, for example, which electric field, together with the axial magnetic field, causes the electrons from the cathode 2 to execute spiral paths of increasing radii, extracting energy from said electric field, as described above. If no means is provided for changing the total energy in the beam, the rotating beam will pass on between the output plates II and I2 and give up the energy absorbed from the input electric field to the electric field induced between the output plates, which are coupled to a load by means of an output transformer IT, for example.

In accordance with my invention, in order to change or vary the energy being transferred, I establish a radially-directed constant electric field in the region between the input plates 9. l9 and the output plates |2, which radial field may be produced by a constant potential difference maintained between cylindrical electrodes, such as a coaxial cylinder and rod, or by an electrostatic lens. In Fig. 1 are shown a cylindrical rod 2|) and cylinder 2| of suitable radii and axial length mounted coaxially on the beam axis ZZ by any suitable means (not shown).

In the operation of the embodiment of my in-- vention shown in Figs. 1-4, the cathode 2 is connected to the negative terminal of a direct current source, such as the battery 25 shown, the output plates 9, III and collector l3 are connected to the highest positive potential, the grid 5 is connected through a modulating signal input coil 25 and a grid leak 21 to a comparatively low positive potential, the accelerating electrode 6, plates 9, HI and rod 2|] are connected to intermediate positive potentials (which may be the same for each), and the cylinder 2| is connected to a high positive potential which may be the same as the plates l2 and collector l3. Preferably, all of the biasingpotentials except those of the oathode and collector are adjustable. The successive potentials of the various electrodes along the beam axis should be either the same or increasing, as shown.

The radial electric field tends to continuously accelerate the electrons in the beam outwardly toward the outer cylinder 2|, but the magnetic field extending perpendicular to the outward motion of the electrons deflects the latter at right angles to the electric and magnetic fields and hence exerts a constraining force which translates a part of the radial velocity into tangential velocity. As a result the electrons acquire an increase in tangential velocity and kinetic energy as they pass through the radial field without any change in their axial velocity in the direction of the magnetic field. If the radial field is of proper axial length the electrons emerge with zero radial velocity. As the electrons pass through the output region they give to that region the energy they received from the D.-C. radial field as R. F. energy along with the R. F. energy acquired from the input R. F. electric field In Fig. 1, I have shown the position of the electron beam at the instant that an electron a enters the cylinder 2| by parallel dash lines 30, and the approximate path of a representative electron a throughout the entire system by the heavy dotted line 32. Under ideal conditions, with abrupt discontinuities in the electric fields between the various regions, the path of each electron from the cathode 2 would be linear along the Zaxis to the plates 9, I0, spiral between these plates, helical in the space between the plates 9, I0 and the cylinder 2| and rod 20, an increasing spiral (or similar) within the cylinder 2|, helical about a new axis parallel to and spaced from the axis ZZ between the cylinder and the plates 12, a decreasing spiral about the new axis between the output plates, and then (if all the spiral energy has been absorbed) a straight line along the new axis to the collector l3. For convenience of illustration only, the parts as shown in Fig. 1 are so proportioned that the axial lengths of the input and output plates are each equal to the axial distance traveled by an electron during five half cycles and the distance between the cylinder 2| and each of the two sets of plates corresponds to a half cycle of the operating frequency. The axial length of the cylinder 2| (and rod 20) is arbitrarily chosen equal to the electron travel during a, half cycle of the electron path in the cylinder. The subscripts 1, 3, 5 etc., are used to identify the conditions at the transverse planes 1, 3, 5 etc, through the positions a1, a3, a5 etc., along the beam path, as shown. I shall assume abrupt discontinuities between the various interaction regions as a first approximation, and then attempt to show that these restrictions do not seriously affect the actual operation.

l'irst consider the problem of the motion of an electron in crossed electric and magnetic fields.

Assume an electric field E sin not is uniform over the volume occupied by the trajectories of the electrons under consideration. Let the vector E be parallel to the Y-axis over the entire volume. Let the uniform magnetic fleld'be parallel or antiparallel to the Z-axis and assume that all of the electrons enter the region of E abruptly with initial velocities no in the y direction, on in the x direction and v in the z direction.

The equations of motion yield the solutions:

when

where to is the time or value of if when an electron entered the region of E sin wt, and =o0o.

In the problem under consideration the electrons travel along the Z axis with velocity v' and enter the input region B sin wt with #n=vo=0. Then If the transit angle through the E sin nut is 1121, where n is an integer, then In cylindrical coordinates with radius r and angle e and the Z axis extended, these coordinates become T=11A21r and e. =0o, since e can be measured from an arbitrary plane, and 2:0.

The tangential velocity of each electron entering the radial field at m on radius 11 is vi=nw, and its spiral energy is W1: mv1'= mrflw If the electrons now enter a unidirectional radial electric field, set up by a potential V bev tween a rod of radius R, and a concentric cylinder of radius Re extending along the Z-axis, the equations of motion in cylindrical coordinates are:

and

/ d d (r'e) rwr z=v't (a new time scale) where eV m 10 84 R The initial conditions for the electrons are r =nA2r 4 s. O, i; o By integration and substitution u r v,= 1z(1 Each electron will continue in the Z direction with the same axial velocity v' and the tangential velocity U3- Each's piral has a circular crosssection with a new axis such as AA, Fig. 1 parallel to the Z-axis and displaced therefrom by a distance R r z D=R-n=R- (1+ and a radius The angular coordinate of the new axis is Now h! T]: J; (1 +;,-)d

is a constant for all electrons and therefore The length I. of the cylinder or radial electric field region is 0'1.

Thus the electrons emerge from the radial electric field region with an angular velocity i w T 2 a radial coordinate R, and angular coordinate e'=5+01. v

'Since a is a constant, we can resolve the angular velocity into rectangular components for any electron represented by without loss generality, where to represents the time the electron enters a new region or leaves the radial field.

If the electrons now pass between the parallel plates of a loaded output system, they satisfy 1 the necessary conditions for giving up their spiral energyto the output circuit to be dissipated in the load. The gain of the amplifier is found by dividing the output energy by the input energy, or

region the main distortions in the field are near the axis where no electrons emerge. Furthermore, the phase of the field in the output region is such that the electrons enter the output region at times and places when the eii'ects of the fringe field due to the radio frequency voltage on the plates are a minimum. That is, the electrons which enter closest to the parallel plates enter when the field is zero.. Those which enter at wt=90 later enter in a maximum field but halfway between the plates so the fringe' field effects are also a minimum at this time.

Fig. 2 shows the axial projection of the path I! of electron a of Fig. 1 from the point do corresponding to a half cycle before leaving the plates S, III to the point as where the electron emerges from the cylinder at a distance R from the Z axis. As explained above, for optimum results the voltage V is adjusted so that the electron arrives at the point as with zero radial velocity and a tangential velocity 9 L v, R(1+ It is not essential or desirable that the transit time of the electrons through the cylinder be exactly a half cycle as illustrated, but instead, there may be several cycles or half-cycles, provided the electrons emerge at zero radial velocity at a comparatively large distance R from the axis.

Fig. 3 shows the axial projection of the circular path of electron a of radius 111 on axis A--A between points as and as. and the spiral path of decreasing radii from the points as to point (115, where the electron leaves the output region and approaches the collector.

Fig. 4 shows the axial projection of the circular paths of four electrons a. b, c and d, spaced 90 apart along the original beam, tween the cylinder II and the plates II, II. A quarter cycle after electron a emerges from the radial field at as this electron reaches point at and electron b emerges at point b3. Similarly, at quarter cycle intervals thereafter electrons c and d emerge at points oz and d3, respectively. Considering all of the electrons in the original rotating beam, electrons will emerge from the radial field at all points on a circle of radius R and whose center lies on the Z axis, under the above conditions, and will enter the output system on a circle centered on the Z axis whose radius lies between limits R and 2r:R, depending on the transit time between the cylinder and the output plates. If all the spiral energy is given up to the output system, all the electrons will strike the collector is on a circle, of radius D=R-1 passing through the various spiral axes A, B, C,D etc., of the electrons.

in the space beradius of the aperture ll For optimum gain, the radius 11 of rotation of the beam when entering the radial field should be small compared to the distance R. Hence, the diameter of the rod 20 should be as small as practicable, and the radius R4: of the cylinder should be comparatively large. In'the example shown, B has been arbitrarily made five timu n. in which case =0.52w, r==0.52R. and the theoretical gain is 6.86. However, it is obvious that in practice the ratio of R to n would be many times that shown, giving a correspondingly higher gain. As can be seen from the formula for the gain above, the gain varies approximately with the square of the ratio R/ n, for large ratios.

The invention has been shown and described first as appliedto the problem of amplifying a radio frequency signal in a spiral beam coupler which employs a grid to modulate the density of the beam. 1 However, the invention is also applicableto many other uses. For example, a premodulated radio frequency signal may be applied to the input plates to generate the spiral beam, which may be amplified by a radial electric field, without any change in structure. For this use the grid 5 of Fig. 1 is not used, and may be omitted if desired, as shown in Fig. 5. The applied signal may be modulated in either frequency or amplitude.

The amplitude modulation on an amplitudemodulated input signal wave varies the input radio frequency field, which causes 1'1 to vary at the modulation frequency. Since the gain of the amplifier decreases as n is increased in accordance with the gain formula given above. and vice versa, the amplification of the modulation will not be linear, so that the per cent modulation on the output wave will be different from that on the input wave. For example, doubling the input amplitude reduces the ratio R/rr, which reduces the gain. In this case the modulation will be amplified less than the carrier, thus producing a lower per cent modulation on the output wave.

In order to improve the depth of amplitude modulation on the carrier in the output, a conducting ring or disc may be provided in the region between the radial field and the output plates, to cut 011' part or all of the electronbeam during a portion of the modulation cycle, and thus vary the number of electrons reaching the output re gion. In Fig. 5, a ring 40 is provided for this purpose having any desired inner diameter. The paths of two electrons a and c emerging from the cylinder on opposite sides are shown, to obtain the outer envelope of the unmodulated beam. The of ring 40 is shown equal to the outer envelope of the unmodulated amplified beam, so that only the outer electrons corresponding to the positive half of the modulation wave will be intercepted. By providing the inner edge of the intercepting ring with notches, serrations or the like of suitable shape, the output can be made substantially a linear function of the input. Fig. 6 shows an example of such a ring 40' having inner teeth II. The ring III is maintained at a potential approximately equal to that of the cylinder 2|. Fig. 7 shows the use of an inner solid disc 40" to intercept the inner portion of the beam. Obviously,.this disc may be serrated, or the like, like The ring ll of Fig. 5 also serves as a shield betweenthe cylinder 2| and the output region, and may be provided for that purpose only. In Fig. 5, a conducting ring 45, at approximately the same potential as the rod 20, is provided bethe ring ll) of Fig. 6.

9 tween the input plates 8, l and the cylinder 2| to serve as a shield.

For a frequency modulated input signal of constant amplitude the beam radius 1'1 entering the radial field and the gain are constant, hence the signal will be amplified and faithfully reproduced in the output system. Moreover, if the output be made substantially independent of the input over some range of input, the output amplitude will not be affected ap creciably' b"; fading in the F. M. signal, thus producing a limiting action. There is an automatic phase lock between the output and input. Thus, a single tube takes the place of a phase-discriminator tube and an F. M. magnetron in F. M. communication systems.

The radial electric field between the rod 20 and cylinder 2| may also be employed, in lieu of the grid 5 of Fig. 1, to amplitude modulate an unmodulated electron beam generated by a radio frequency carrier input to the plates 8, "I. For this purpose, the radial electric field may be varied or modulated above and/or below a given biasing potential, as by inducing a modulating signal voltage in a coupling coil 26'. In this case the input radius n is constant and the distance R. is varied by the modulating voltage. When the modulating voltage raises the potential of the cylinder 2l,'the energy level of the beam is increased, and vice versa, producing a corresponding variation in the output power.

When amplification as well as modulation is desired the biasing potential on the cylinder 2| is made high compared with that of the rod 20, as shown in Fig. 1.

When modulation without amplification is desired the cylinder and rod are both maintained at the beam potential and the electron beam is subjected only to the alternating radial electric field produced by the modulating signal voltage. As a modulator alone, the structure of Fig. 5 or Fig. 6 can be employed. However, for 100% amplitude modulation the distance R should vary between zero and approximately twice the radius 11 at the entrance to the cylinder. Therefore. the transverse dimensions of the input and output regions are preferably more nearly equal, as in the grid modulated spiral beam coupler of the above-mentioned Cuccia application. Such a structure is illustrated in Figs. 8, 9, and 10. In this modification the input and output regions are provided by cavity resonators with coaxial line input and output coupling means, especially adapted for use at high or microwave frequencies. It is to be understood that suitable cavity resonators and coupling means may be incorporated in the amplifier structures of the embodiments of my invention shown in Figs. 1 through 7, for high frequency applications.

In Figs. 13-10, a cylindrical metallic envelope II is closed at each end by plates SI and 52 to complete a vacuum enclosure. A cylindrical input cavity resonator 54 having apertured end plates 55 and 58 is supported in spaced relation to and coaxially within one end of the envelope 5. by means of a ring 51, insulators 58 and 59, and bolts 60, as shown. A pairof arcuate input plates 82 and 83 are mounted by supports 64 in opposing relation coaxially within the resonator 54. The other end of the envelope 50 provides an output resonator 65. A pair of arcuate output plates 68 and 61 are mounted by supports 88 in opposing relation coaxially within the output resonator 65. A shielding ring 89 completes the resonator 65. To further eliminate undesired coupling between the input and output 10 fields, the output plates 88 and 81 may be disposed at right angles to the'input plates 02 and 63, as shown in the drawing. The resonators 54 and 65 are resonant at the operating frequency. The end plate 52 also serves, as the beam collector.

A cylinder 10, of substantially the same radius as the arcuate plates 62, 83, 88 and 61 is mounted eoaxially in the space between the input and output systems by suitable means such as a rod 'll secured in insulated relation to the envelope 50 and a second rod 12 extending through a seal 13 in the opposite wall of the envelope. A cylindrical rod 15 is mounted concentrically with the cylinder ID as by a small rod 16 extending through a seal 11 in the envelope wall. A conventional electron beam gunis mounted in insulated relation on the plate 55 in position to project an electron beam along the axis through the two resonators and the radial field region. The input resonator 54 is provided with an input coupling loop 85 extending transversely of the plates 62 and 53, for coupling with the axial magnetic component of the electromagnetic field adjacent one of the gaps between the plates. and connected to the inner and outer conductors 8G and 81 of a coaxial transmission line. Similarly, a coupling loop 88 is provided in the output resonator 65 connected to a coaxial transmission linev 89, 90. A constant magnetic field H is established along the axes by suitable means (not shown).

In the operation of the device shown in Figs. 8-10 as a modulator, suitable operating potentials are aplied to the electro gun 80, resonator 54, and envelope 50. Thus the resonator 54 and plates 62 and 63 have the same biasing potential, and the envelope 50, resonator 55, plates 65 and 67 and collector 52 are at the same potential. The cylinder 10 and rod 15 are biased at the same potential through the center tap of a coupling coil connected across the supporting rods 12 and 16 which serve also as leads.

A high frequency carrier is coupled into the input resonator by the loop 85 to excite the resonator and establish a high frequency electric field between the plates 82 and 63. The electrons from the gun 80 are caused to spiral and enter the radial field on some radius 11. A modulating signal voltage is impressed between the cylinder 10 and rod 15 by means of the coupling coil 95 to increase or decrease the energy and path radius of the spiralling electrons. For modulation the amplitude of the modulating voltage should be suilicient to absorb all of the spiral energy abstracted from the input field, when the voltage is at its negative maximum. Then the inner and outer envelopes oi the modulated beam would be approximately as shown by the dash lines 81 and 98, respectively. As in the other forms of my' invention, the aperture of the plate 69 may be made smaller, and may be serrated, to intercept a portion of the modulated beam, if desired. Also, the aperture in the plate 56 may be reduced, as in Fig. 5, for better shielding.

When the defiecting plates of the resonators are curved in the sense that the R. F. field exists across gaps, as in Figs. 8-l0, electrons in various portions of the space will not couple equally to the field as they would with parallel fiat plates. Therefore, the emciency of the device might be lower in the case of certain types of orbits. However, the use of gaps in the output system would means that the output would be 11 I a more sensitive function of the distances of the electrons from the gaps, hence a more sensitive function of the input, and the device would approach more closely to being a linear amplifier.

I have used the term amplifie for all the devices of Figs. 1-7, even though the output wave is not an amplified form of the input wave to the plates 9, l when the input wave is supplied by a local oscillator. Such a device might not be considered an amplifier in the usual sense. However, the output of the local oscillator is amplified. Even when used as a modulator only, as shown in Figs. 8-10, the device is an amplifier during the positive half and a deamplifier during the negative half of the modulating signal wave. Broadly speaking, therefore, I have invented a novel method and means for changing or varying the total energy possessed by the spiralling electrons of a spiral beam type electron discharge device, either for amplification, de-amplification, modulation, or other analogous purpose.

While I have indicated the preferred embodiments of my invention of which I am now aware and have indicated only a few specific applications for which the invention may be employed, it will be apparent that the invention is by no means limited to the exaict forms illustrated or the use indicated, but that many variations may be made in the particular structures used and the purpose for which it is employed without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. An electron discharge device includin means for generating a radio frequency rotating-pencil beam of electrons spiralling about a given axis at constant angular velocity, the spiral energy of each electron being a function of the radius of curvature of the spiral path at any instant, output means coupled to said beam of spiralling electrons for extracting energy therefrom, and means coupled to said beambetween said beamgenerating means and said output means for changing the spiral energy of said beam.,

2. An electron discharge device including means for generating a radio frequency rotating-pencil beam of electrons spiralling about a given axis at constant angular velocity, the spiral energy of each electron being a function of the radius of curvature of the spiral path at any instant, output means coupled to said beam of spiralling electrons for extracting energy therefrom, and means coupled to said beam between said beam-gencratin means and said output means for increasing the spiral energy of said beam, whereby said device functions as an amplifier.

3. An electron discharge device according to claim 1, including means for establishing a. constant magnetic field extending along all three of said means and parallel to said axis.

4. An electron discharge device according to claim 3, wherein the strength of said magnetic field is equal to where w is the angular frequency of said radio frequency field, and m and e are the mass and electric charge of an electron.

5. An electron discharge device according to claim 1, wherein said beam generating means and said output means comprise cavity resonators,

6. An electron discharge device including means for generating and directing an electron beam along a given axis, means for establishing a constant magnetic field substantially parallel with said axis, input means for establishing a radio frequency electric field transverse to said axis and to said magnetic field for causing the electrons of said beam to traverse spiral paths having increasing radii dependent upon the energy absorbed from said electric field, output means subjected to said magnetic field and coupled to said beam of spiralling electrons for abstracting energy therefrom, and means subjected to said magnetic field and coupled to said beam between said input means and said output means for changing the spiral energy of said beam.

7. An electron discharge device according to claim 6, wherein said last-named means includes means for modulating the energy of said beam.

8. An electron discharge device according to claim 7, further including a member arranged between said energy changing means and said output means, for intercepting a portion of said beam when said beam is modulated by said modulating means.

9. An electron discharge device according to claim 8, wherein said member is provided with a serrated edge.

10. An electron discharge device according to claim 6, wherein said last-named means comprises means for establishing a transverse-component electric field in the path of said beam.

11. An electron discharge device according to claim 10, wherein said last-mentioned field is a radial field established between a cylinder and a rod coaxially disposed on the axis of said beam.

12. An electron discharge device according to claim 6, wherein said last-named means comprises means for establishing an alternating transverse-component electric field in the path of said beam.

where w is the angular frequency of said radio frequency electric field, and m and e are the mass and electric charge of an electron.

16. An electron discharge device according to claim 6, wherein said last-named means comprises means for establishing a transverse-component, unidirectional electric field in the path of said beam and means for modulating said unidirectional field.

17. An electron discharge device according to claim 16, including a member arranged between said energy changing means and said output means for intercepting a portion. of said beam when said field is modulated.

18. An electron discharge device according to claim 6, wherein said input means comprises an amplitude modulated signal, said device including a member arranged between said energy 13 a changing and said output means for intercepting a portion of said beam.

19. A method ofamplifying a radio frequency signal comprising the steps of generating a beam of electrons rotating about a given axis at the signal frequency in spiral paths having radii proportional to the amplitude of said signal, subiecting said rotating beam to a radial direct cur rent field from which energy is extracted by the spiralling electrons to increase the radii ofsaid paths. and then causing said spirallin electrons to give up their total energy to an output system.

20. A methodof amplifying 'a radio frequency signal comprising the steps of generating and directing a beam of electrons along a given axis, subjecting said beam to a radio frequency electric field proportional to said signal and transverse to said axis and a constant magnetic fleld'substantially parallel to said axis for causing said electrons to traverse spiral paths of increasing radii around said axis, subjecting said spiralling electrons to a radial direct current field for further increasing the spiral path radii, and extracting amplified energy from said spirallin electrons.

JOHN S. DONAL, .111.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,200,745 Heymann May 14, 1940 2,237,671 Kallmann Apr. 8, 1941 2,295,315 Wolf Sept. 8, 1942 2,328,259 Christaldl et a1 Aug. 31, 1943 2,376,707 McCoy May 22, 1945 2,480,978 Sunstein Sept. 6, 1949 

